This invention relates generally to turbines, and more specifically, to exhaust hoods used with turbines.
Known steam turbine low pressure sections include an exhaust hood/diffuser that is coupled downstream from a last stage of the turbine. The exhaust hood enables static pressure of the steam to be recovered and guides the steam from the last stage to a condenser. Specifically, steam from the last stage is channeled to the condenser through the exhaust hood. Often steam discharged from the last stage has a high swirl and high flow gradient in radial direction. Moreover, a portion of the steam flows directly to the condenser through a lower half of the exhaust hood and the remaining steam travels through an upper half of the exhaust hood.
Typically, steam flowing through the upper half of the exhaust hood is turned 180° from a vertically upward flow direction to a downward flow direction and into the condenser. The change in the flow direction of the steam may generate a strong vortex behind a steam guide in the upper half of the hood. The vortex minimizes an effective flow area between the steam guide and an outer wall of the hood. Accordingly, flow losses in the steam path are increased, such that flow diffusion in the upper half of the exhaust hood is decreased. As such, known steam turbine hoods may decrease the performance of the turbine.